/**
 * @param {number} numBottles 你买的饮料
 * @param {number} numExchange 空瓶/饮料汇率
 * @return {number}
 */
var numWaterBottles = function (numBottles, numExchange) {
    let canyou = numBottles;
    let kongb = numBottles;
    while (kongb >= numExchange) {
        kongb -= numExchange;
        canyou++;
        kongb++;
    }
    return canyou;
};